Two isotopes 'P' and 'Q' of atomic masses 10 and 20, respectively, are mixed in equal amount, by mas — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

Let initial masses be $m_0$. After 20 days (2 half-lives for P), P's remaining mass is $m_0/4$. Mass ratio $P:Q$ becomes $(m_0/4) : m_Q = 1:4$, yielding $m_Q = m_0$. Q's mass did not decrease, meaning it did not decay. Thus, its half-life is infinite. Therefore, correct answer is D.